The T lymphocyte compartment of the immune system can be divided into a variety of cell subsets. For example, CD4+ T cells represent the T helper cell subset, whereas CD8+ T cells represent the cytotoxic T cell subset. Additionally, CD4+ T helper cells mature into distinct subpopulations that produce different panels of cytokines: the T helper type 1 (Th1) subset produces interleukin-2 (IL-2), interferon-γ (IFN-γ) and tumor necrosis factor-β (TNF-β), whereas the T helper type 2 (Th2) subset produces interleukin-4 (IL-4), interleukin-5 (IL-5), interleukin-6 (IL-6) and interleukin-10 (IL-10). The Th1 and Th2 subsets also have differing functional activities. Th1 cells are involved in inducing delayed type hypersensitivity responses, whereas Th2 cells are involved in providing efficient “help” to B lymphocytes and stimulate production of IgG1 and IgE antibodies. For a review of Th1 and Th2 subsets, see Seder, R. A. and Paul, W. E. (1994) Ann. Rev. Immunol. 12:635-673.
Cytokines are thought to play a dominant role in controlling the differentiation of T helper precursors (Thp) to either the Th1 or Th2 lineage. Th1-associated cytokines, such as IFN-γ, can enhance the development of Th1 cells and inhibit the development of Th2 cells, whereas Th2-associated cytokines, such as IL-4 and IL-10, can enhance the development of Th2 cells and inhibit the development of Th1 cells. Thus, cytokines can reciprocally regulate the development and/or progression of either a Th1 or a Th2 response.
The course of certain disease states is influenced by whether a predominant Th1 response or Th2 response is mounted. For example, in experimental leishmania infections in mice, animals that are resistant to infection mount predominantly a Th1 response, whereas animals that are susceptible to progressive infection mount predominantly a Th2 response (Heinzel, F. P., et al. (1989) J. Exp. Med. 169:59-72; Locksley, R. M. and Scott, P. (1992) Immunoparasitology Today 1:A58-A61). In murine schistosomiasis, a Th1 to Th2 switch is observed coincident with the release of eggs into the tissues by female parasites and is associated with a worsening of the disease condition (Pearce, E. J., et al. (1991) J. Exp. Med. 173:159-166; Grzych, J-M., et al. (1991) J. Immunol. 141:1322-1327; Kullberg, M. C., et al. (1992) J. Immunol. 148:3264-3270). Many human diseases, including chronic infections (such as with human immunodeficiency virus (HIV) or tuberculosis) and certain metastatic carcinomas, also are characterized by a Th1 to Th2 switch, with elevated expression of IL-10 (see e.g., Shearer, G. M. and Clerici, M. (1992) Prog. Chem. Immunol. 54:21-43; Clerici, M and Shearer, G. M. (1993) Immunology Today 14:107-111; Yamamura, M., et al. (1993) J. Clin. Invest. 91:1005-1010; Pisa, P., et al. (1992) Proc. Natl. Acad. Sci. USA 89:7708-7712; Fauci, A. S. (1988) Science 239:617-623). Furthermore, certain autoimmune diseases have been shown to be associated with a predominant Th1 response. For example, patients with rheumatoid arthritis have predominantly Th1 cells in synovial tissue (Simon, A. K., et al. (1994) Proc. Natl. Acad. Sci. USA 91:8562-8566) and experimental autoimmune encephalomyelitis (EAE) can be induced by autoreactive Th1 cells (Kuchroo, V. K., et al. (1993) J. Immunol. 151:4371-4381).
Velupillai and Ham (Proc. Natl. Acad. Sci. USA (1994) 91:18-22) have shown that schistosome egg antigen (SEA), which expresses the Lewisx antigen, and conjugates of the Lewisx antigen, can stimulate IL-10 production by B cells from Schistosoma mansoni infected mice, but not B cells from uninfected mice, suggesting that during the course of S. mansoni infection, the observed Th1 to Th2 shift may results from IL-10 production by B cells induced by SEA. This work, however, did not demonstrate whether human immune cells (e.g., human immune cells in the absence of S. mansoni infection) were responsive to Lewis antigen-containing compounds, nor whether cell types other than B cells, such as macrophages or T cells, could produce IL-10 in response to stimulation with compounds comprising a Lewis antigen in the absence of S. mansoni infection. Moreover, this work did not demonstrate whether production other cytokines that regulate development of Th1 and Th2 responses, such as IL-4, could be stimulated